1. Field of the Invention
This invention relates to a monitoring device for power presses, and particularly to a true-hit counter for counter only workpieces actually formed.
2. Description of the Prior Art
A typical power press comprises a frame structure or body which provides a feed path for the stock between relatively moveable tool-carrying members so that tools or dies carried by the latter can act on the stock and be released Therefrom successfully in consequence of the relative movement of the tool-carrying members. One of the tool-carrying members is normally constituted by a slide or ram moveable rectilinearly along a guide path defined by guide means provided for the ram along the frame structure in a direction toward and away from the tool-carrying members constituted by a bed or table on the frame structure. The driving means for the ram comprises a flywheel or other rotary power storage member operatively connected through a clutch with an eccentric element such as a crank, cam or eccentric serving to impart the required movement to the ram. The rotary powered storage member (flywheel) is driven by an electric motor which is the prime energy source for the press.
Many power presses tend to work at a very high speed, producing thousands of workpieces in a day. It is, of course, most important to have some kind of automatic means for providing an accurate count of the actual number of workpieces produced so that the machine can be shut down when a given order has been completed. In view of the manner in which the workpieces are released from the press, it is very difficult to arrange a counting device which will detect and count the work pieces themselves. Because of this difficulty, a system frequently used is to provide a counter which counts each cycle of the ram, it being assumed that one workpiece is produced in each cycle. However, this does not take into consideration the fact that there may be frequent "air hits," i.e. cycles in which there is no metal present between the dies so that noe workpiece is actually produced.
Another problem with power presses is that of an improper or dangerous operation, such as bearing seizure, double hit or over-sized stock. Serious damage to the press is avoided in such situations only by the quick, and sometimes dangerous, action of the press operator. Thus, there is need not only for a system to count workpieces actually produced but to generally monitor and control the operation of a power press.
It is, therefore, the object of the present invention to provide a system which will accurately count only workpieces which are actually formed by a power press and monitor energy lost by forming as well as forces working on the press and die parts.